1. Technical Field
The present invention relates to a control device for a touch panel.
2. Background
Touch panel is popularly used in appliance, communication device and electrical information device. Touch panel is usually used as input interface, such as personal digital assistant (PDA), electrical product and games. Today, the integration trend of touch panel and display screen can allow user to choose icon shown on the screen by finger or stylus, then personal digital assistant, electronic product and games can execute favorite function. Such touch panel can also used in public information inquiry system, then the public can operate the system more efficiently.
FIG. 1 shows a schematic diagram of a touch panel 10 according to the prior art. The touch panel 10 comprises a plurality of X-directional sensing lines X1-Xm and a plurality of Y-directional sensing lines Y1-Yn, wherein m and n are different or identical positive integer. The X-directional sensing lines X1-Xm and the Y-directional sensing lines Y1-Yn are buried on different layers of the touch panel 10. Referring to FIG. 1, the X-directional sensing lines X1-Xm and the Y-directional sensing lines Y1-Yn are arranged in an interlaced manner to form a sensing grid. In the sensing grid, a plurality of mutual capacitor form between each X-directional sensing line and each Y-directional sensing line, and a plurality of parasitic capacitance form between each X-directional sensing line, Y-directional sensing line and ground.
In conventional operation, a driving signal (usually a square wave signal) inputs to the X-directional sensing line or the Y-directional sensing line. A plurality of sensing voltages are generated on corresponding Y-directional sensing line or X-directional sensing line by coupling effect of mutual capacitor. Because the value of the sensing voltage changes by touch condition of the user and sensing line, a touch position of the user can be known by detecting the difference of the sensing voltage.
However, in conventional technology, the driving signal is simultaneously applied to all X-directional sensing lines or Y-directional sensing lines on the touch panel, then the delay time is pretty long based on the parasitic capacitance and a resistance of sensing line, and seriously affects the operation frequency of the driving signal and the detection time of the sensing voltage, and degrade with the increasing of the size of the touch panel. Therefore, a control device for the touch panel is used to improve the previous problem.